Evaluation of the Use of Steel Bracing to Improve Seismic Performance of Reinforced Concrete Building

Abstract

The aim of this paper is to evaluate the possible improvement of seismic performance of existing reinforced concrete building (the 5th Building of UNS Engineering Faculty) by the use of steel bracing. Three methods of seismic evaluation are employed for the purpose of the study i.e. Nonlinear Static Pushover Displacement Coefficient Method as described in FEMA 356, Improvement of Nonlinear Static Pushover Displacement Coefficient Method as described in FEMA 440 and dynamic time history analysis following the Indonesian Code of Seismic Resistance Building (SNI 03-1726-2002) criteria. The results show that the target displacement determined from nonlinear pushover analysis of the existing building in X direction is 0.188 m and in Y direction is 0.132 m. The performance of this building could be categorized in between Life Safety (LS) - Collapse Prevention (CP) and plastic hinges occur in columns. It is also indicated that the story drifts in Y direction exceed the serviceability limit criterion when the recorded El Centro accelerogram was used for dynamic time history analysis. The performance of the existing building could be improved if steel bracings are utilized for seismic retrofitting. It is shown from the nonlinear pushover analysis that target displacements in both directions are reduced by 16%-55% if the proposed steel bracings are used. Furthermore, dynamic time history analysis points out that the story drifts of the retrofitted building are within the limit criteria. Meanwhile, the size of steel bracing elements do not significantly affect the seismic performance of retrofitted building.